[R-390] 3TF7 Substitutes

[David Wise]

> -----Original Message-----
> From: mikea [mailto:mikea at mikea.ath.cx]
> Sent: Friday, September 24, 2004 10:29 AM
> To: r-390 at mailman.qth.net
> Subject: Re: [R-390] 3TF7 Substitutes
> cause of this drift.
> 
> Thanks _very_ much for your research results. I have had the benefit 
> of your expertise for some years now, and think it is appropriate to 
> give you your due in public. 
> 
> I feel some construction coming on.

If you're in the mood for construction and would prefer to make
*no modifications whatsoever* to your radio, you might consider
the 3DW7A, which I designed a while back.  Thanks again to Roy Morgan
for massaging the picture into a portable format.  I tried to post
it here, but the listserv rejected the .jpg attachment.  Contact
me off-list and I'll email it to you.  The single-source items
(the MOSFETs and the RMS converter IC) are available at DigiKey.
Everything else is generic.

It's a cool-running two-pin module, although you'll
need a magnifying glass and tweezers to cram it into
the "tubester" form factor like I did.  Maybe I ought to
post a photo of the completed unit to prove it can be done.

By the way, I'm still working on the 3DW7D, which does the
same job digitally at about 1/2 the parts count.  Somebody
asked for a LED to simulate the olde-tyme glow, and I got
carried away.  Soon (but that means < 5 years :)

73,
Dave Wise (SWL)